SPIFF(1) SPIFF(1)
February 2, 1988
NAME
spiff - make controlled approximate comparisons between files
SYNOPSIS
spiff [ -s script ] [ -f sfile ] [ -bteviqcdwm ] [ -a | -r value ]
-value file1 file2
DESCRIPTION
Spiff compares the contents of file1 and file2 and prints a
description of the important differences between the files. White
space is ignored except to separate other objects. Spiff maintains
tolerances below which differences between two floating point numbers
are ignored. Differences in floating point notation (such as 3.4 3.40
and 3.4e01) are treated as unimportant. User specified delimited
strings (i.e. comments) can also be ignored. Inside other user
specified delimited strings (i.e. quoted strings) whitespace can be
significant.
Spiff's operation can be altered via command line options, a command
script, and with commands that are embedded in the input files.
The following options affect spiff's overall operation.
-q suppresses warning messages.
-v use a visually oriented display. Works only in MGR windows.
Spiff has several flags to aid differencing of various programming
languages. See EXAMPLES for a detailed description of the effects of
these flags.
-C treat the input files as C program source code.
-S treat the input files as Bourne shell program source code.
-F treat the input files as Fortran program source code.
-M treat the input files as Modula-2 program source code.
-L treat the input files as Lisp program source code.
By default, the output looks somewhat similar in appearance to the
output of diff(1). Lines with differences are printed with the
differences highlighted. If stdout is a terminal, as determined by
isatty(), then highlighting uses standout mode as determined by
termcap. If stdout is not a tty, then the underlining (via
underscore/backspace/char) is used to highlight differences. The
following option can control the format of the ouput.
-t produce output in terms of individual tokens. This option is
most useful for debugging as the output produced is verbose to
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February 2, 1988
the point of being unreadable.
The following option controls the differencing algorithm.
-e compare each token in the files with the object in the same
ordinal position in the other file. If the files have a
different number of objects, a warning message is printed and the
objects at the end of the longer file are ignored. By default,
spiff uses a Miller/Myers algorithm to find a minimal edit
sequence that will convert the contents of the first file into
the second.
-<decimal-value>
sets a limit on the total number of insertions and deletions that
will be considered. If the files differ by more than the stated
amount, the program will give up, print a warning message, and
exit.
The following options control the command script. More than one of
each may appear at at time. The commands accumulate.
-f sfile
a command script to be taken from file sfile
-s command-script
causes the following argument to be taken as a command script.
The following options control how individual objects are compared.
-b treat all objects (including floating point numbers) as literals.
-c ignore differences between upper and lower case.
The following commands will control how the files are parsed.
-w treat white space as objects. Each white space character will be
treated as a separate object when the program is comparing the
files.
-m treat leading sign characters ( + and - ) as separate even if
they are followed by floating point numbers.
-d treat integer decimal numbers (such as 1987) as real numbers
(subject to tolerances) rather than as literal strings.
The following three flags are used to set the default tolerances. The
floating-point-numbers may be given in the formats accepted by
atof(3).
-a floating-point-number
specifies an absolute value for the tolerance in floating point
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numbers. The flag -a1e-2 will cause all differences greater than
0.01 to be reported.
-r floating-point-number
specifies a relative tolerance. The value given is interpreted as
a fraction of the larger (in absolute terms) of the two floating
point numbers being compared. Thus, the flag -r0.1 will cause
the two floating point numbers 1.0 and 0.9 to be deemed within
tolerance. The numbers 1.0 and 0.89 will be outside the
tolerance.
-i causes differences between floating point numbers to be ignored.
If more than one -a, -r, or -i flag appear on the command line, the
tolerances will be OR'd together (i.e. any difference that is within
any of the tolerances will be ignored).
If no default tolerances is set on the command line, the program will
use a default tolerance of '-a 1e-10 -r 1e-10'.
SCRIPT COMMANDS
A script consists of commands, one per line. Each command consists of
a keyword possibly followed by arguments. Arguments are separated by
one or more tabs or spaces. The commands are:
literal BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Specifies the delimiters surrounding text that is to be treated
as a single literal object. If only one argument is present, then
only that string itself is treated as a literal. If only two
arguments are present, they are taking as the starting and ending
delimiters respectively. If three arguments are present, they
are treated as the start delimiter, end delimiter, and a string
that may be used to escape an instance of the end delimiter.
beginchar BEGINNING-OF-LINE-CHARACTER
Set the the beginning of line character for BEGIN-STRING's in
comments. The default is '^'.
endchar END-OF-LINE-CHARACTER
Set the end of line character for END-STRING's in comments. The
default is '$'.
addalpha NEW-ALPHA-CHARACTER
Add NEW-ALPHA-CHARACTER to the set of characters allowed in
literal strings. By default, spiff parses sequences of
characters that begin with a letter and followed by zero or more
letters or numbers as a single literal token. This definition is
overly restrictive when dealing with programming languages. For
example, in the C programming language, the underscore character
is allowed in identifiers.
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comment BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Specifies the delimiters surrounding text that is to be be
ignored entirely (i.e. viewed as comments). The operation of the
comment command is very similar to the literal command. In
addition, if the END-STRING consists of only the end of line
character, the end of line will delimit the end of the comment.
Also, if the BEGIN-STRING starts with the beginning of line
character, only lines that begin with the BEGIN-STRING will be
ignored.
More than one comment specification and more than one literal string
specification may be specified at a time.
nestcom BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Similar to the comment command, but allows comments to be nested.
Note, due to the design of the parser nested comments can not
have a BEGIN-STRING that starts with the beginning of line
character.
resetcomments
Clears the list of comment specifications.
resetliterals
Clears the list of literal specifications.
tol [aVALUE|rVALUE|i|d . . . [ ; aVALUE|rVALUE|i|d . . . ] . . . ]
set the tolerance for floating point comparisons. The arguments
to the tol command are a set of tolerance specifications
separated by semicolons. If more than one a,r,d, or i appears
within a specification, then the tolerances are OR'd together
(i.e. any difference that is within any tolerance will be
ignored). The semantics of a,r, and i are identical to the -a,
-r, and -i flags. The d means that the default tolerance (as
specified by the invocation options) should be used. If more
than one specification appears on the line, the first
specification is applied to the first floating point number on
each line, the second specification to the second floating point
number one each line of the input files, and so on. If there are
more floating point numbers on a given line of input than
tolerance specifications, the last specification is used
repeatedly for all remaining floating point numbers on that line.
command STRING
lines in the input file that start with STRING will be
interpreted as command lines. If no "command" is given as part of
a -s or -f then it will be impossible to embed commands in the
input files.
rem
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# used to places human readable remarks into a commands script.
Note that the use of the '#' character differs from other command
languages (for instance the Bourne shell). Spiff will only
recognize the '#' as beginning a comment when it is the first
non-blank character on the command line. A '#' character
appearing elsewhere will be treated as part of the command.
Cautious users should use 'rem'. Those hopelessly addicted to
'#' as a comment character can have command scripts with a
familiar format.
Tolerances specified in the command scripts have precedence over the
tolerance specified on the invocation command line. The tolerance
specified in file1 has precedence over the tolerance specified in
file2.
VISUAL MODE
If spiff is invoked with the -v option, it will enter an interactive
mode rather than produce an edit sequence. Three windows will be put
on the screen. Two windows will contain corresponding segments of the
input files. Objects that appear in both segments will be examined
for differences and if any difference is found, the objects will be
highlighted in reverse video on the screen. Objects that appear in
only one window will have a line drawn through them to indicate that
they aren't being compared with anything in the other text window. The
third window is a command window. The command window will accept a
single tolerance specification (followed by a newline) in a form
suitable to the tol command. The tolerance specified will then be
used as the default tolerance and the display will be updated to
highlight only those objects that exceed the new default tolerance.
Typing m (followed by a newline) will display the next screenfull of
text. Typing q (followed by a newline) will cause the program to
exit.
LIMITS
Each input files can be no longer that 10,000 line long or contain
more than 50,000 tokens. Longer files will be truncated. No line can
be longer than 1024 characters. Newlines will be inserted every 1024
character.
EXAMPLES
spiff -e -d foo bar
this invocation (using exact match algorithm and treating integer
numbers as if they were floats) is very useful for examining
large tables of numbers.
spiff -0 foo bar
compare the two files, quitting after the first difference is
found. This makes the program operate roughly like cmp(1).
spiff -0 -q foo bar
same as the above, but no output is produced. The return code is
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still useful.
spiff -w -b foo bar
will make the program operate much like diff(1).
spiff -a1e-5 -r0.001 foo bar
compare the contents of the files foo and bar and ignore all
differences between floating point numbers that are less than or
equal to 0.00001 or 0.1% of the number of larger magnitude.
tol a.01 r.01
will cause all differences between floating point numbers that
are less than or equal to 0.01 or 1% of the number of larger
magnitude to be ignored.
tol a.01 r.01 ; i
will cause the tolerance in the previous example to be applied to
the first floating point number on each line. All differences
between the second and subsequent floating point numbers on each
line will be ignored.
tol a.01 r.01 ; i ; a.0001
like the above except that only differences between the second
floating point number on each line will be ignored. The
differences between third and subsequent floating point numbers
on each number will be ignored if they are less than or equal to
0.0001.
A useful script for examing C code is:
literal " " \
comment /* */
literal &&
literal ||
literal <=
literal >=
literal !=
literal ==
literal --
literal ++
literal <<
literal >>
literal ->
addalpha _
tol a0
A useful script for shell programs is:
literal ' ' \
comment # $
tol a0
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A useful script for Fortran programs is:
literal ' ' '
comment ^C $
tol a0
A useful script for Modula 2 programs is:
literal ' '
literal " "
nestcom (* *)
literal :=
literal <>
literal <=
literal >=
tol a0
A useful script for Lisp programs is:
literal " "
comment ; $
tol a0
DIAGNOSTICS
Spiff's exit status is 0 if no differences are found, 1 if differences
are found, and 2 upon error.
BUGS
In C code, escaped newlines will appear as differences.
Comments are treated as token delimiters.
Comments in Basic don't work right. The line number is not ignored.
Continuation lines in Fortran comments don't work.
There is no way to represent strings specified using a Hollerith
notation in Fortran.
In formated English text, hyphenated words, movements in pictures,
footnotes, etc. will be reported as differences.
STRING's in script commands can not include whitespace.
Visual mode does not handle tabs properly. Files containing tabs
should be run through expand(1) before trying to display them with
visual mode.
In visual mode, the text windows appear in a fixed size and font.
Lines longer than the window size will not be handled properly.
Objects (literal strings) that contain newlines cause trouble in
several places in visual mode.
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Visual mode should accept more than one tolerance specification.
When using visual mode or the exact match comparison algorithm, the
program should do the parsing on the fly rather than truncating long
files.
AUTHOR
Daniel Nachbar
COPYRIGHT
Copyright (c) 1988 Bellcore
All Rights Reserved
Permission is granted to copy or use this program,
EXCEPT that it may not be sold for profit, the copyright
notice must be reproduced on copies, and credit should
be given to Bellcore where it is due.
BELLCORE MAKES NO WARRANTY AND ACCEPTS
NO LIABILITY FOR THIS PROGRAM.
SEE ALSO
atof(3) isatty(2) diff(1) cmp(1) expand(1) mgr(1L)
"Spiff -- A Program for Making Controlled Approximate Comparisons of
Files", by Daniel Nachbar.
"A File Comparison Program" by Webb Miller and Eugene W. Myers in
Software - Practice and Experience, Volume 15(11), pp.1025-1040,
(November 1985).
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